AUBURN, Ala.—Dan Holt and Carol Johnston, researchers in Auburn University’s School of Fisheries, Aquaculture and Aquatic Sciences, have discovered evidence that fish—like mammals and birds—raise their voices when communicating in noisy settings. This reaction, known as the Lombard effect, has never before been documented in fish. The discovery is an important step toward determining how human-generated noise affects the reproductive success and growth rates of fish, the main dietary protein source of 1 billion people worldwide.
Holt and Johnston studied the effects of elevated noise on the communication of the male , or blacktail shiner, a freshwater fish common in the Southeast. By observing the fish in a laboratory under both quiet and noisy conditions, the researchers were able to study how the males’ communication and behavior were affected by elevated sound levels. They watched to see whether the fish would move closer to one another, repeat themselves or raise their voices in order to compensate for the additional sound. The discovery that the fish adjusted the volume of their communication was a pleasant surprise to the researchers.
“Every human does this—when you’re in a loud room, you elevate the amplitude of your voice in order to communicate with someone,” said Holt, a post-doctoral researcher. “This is evidence that fish do the same thing, and because it’s the first time this has ever been documented in fish, it is very exciting to us.”
In the future, researchers in Johnston’s lab plan to build on the discovery by studying how noise may affect fishes’ growth rates or their reproductive success, two activities that are critical to the propagation of species. They also plan to look at how noise affects species other than the blacktail shiner.